The present disclosure relates generally to rotational electric actuators. More particularly, it relates to modular actuators for manmade or artificial limbs for robotic prosthetic or orthotic devices, and the like.
Prior art prosthetic robotic arms cannot produce torque, strength, or lift capability comparable to a human arm within the dimensions and weight of the average human arm. Stated differently, prosthetic robotic arms simply do not have the same power density as does a human arm. The electromechanical devices which drive the prior art robotic limbs are bulky, heavy, and inefficient. Moreover, these prior art limbs require generous power sources which typically involves the use of numerous batteries or bulky external power supplies thereby further adding to the weight of the system. Such increased weight limits the portability and ergonomics of a prosthetic or robotic limb.
In addition, limbs such as arms, whether for prosthetics or robotics, are assembled with custom bolted and screwed mechanical connections that are different for each joint. These mechanical connections may or may not include the electrical interconnections between adjacent arm components. Typical solutions can include complex wiring harnesses that require bulky electrical connectors or solder connections. Such solutions are disadvantageous because they only work for a specific joint. In other words, they are not usable for joints between multiple arm modules.
Although prosthetic technology has advanced in recent years, the prior art still has failed to bridge the gap between manmade prosthetics and user demands and needs. Therefore, an extensive opportunity for design advancements and innovation remains where the prior art fails or is deficient. Most myoelectric prosthetic arms move in three ways. They bend at the elbow, rotate at the wrist and a rudimentary hand clamps shut. A need exists to replicate the great many varieties of movements that a human arm is capable of making. It is believed that a human arm has 27 degrees of freedom, including individual finger bending, and the use of an opposable thumb. Robotic arms used as prostheses are not fully articulated to give the user the same degrees of freedom as a natural arm, not to mention the speed and torque of a human arm. Moreover, the human arm can sense pressure, which conventional man-made arms cannot do. It would be advantageous if the prosthetic or robotic arm was sensitive enough to pick up a piece of paper, a wine glass, or even a grape yet powerful enough to handle the lifting of moderate to heavier weight items without mishap.
While many advances have taken place to allow for better prosthetics and orthotics, as well as more functional robotic limbs, there remains a need to develop more compact, lightweight, and powerful high torque limb drives. In addition, there exists a need to connect the various segments of a limb to the limb drives so that the segments can be more readily attached and detached in a simple manner, without external wiring, and in a manner that provides a weather tight seal. It would also be advantageous to provide integral torque and/or position sensing for determining the loads and stresses in the limb as well as the relative positioning of the individual limb segments, and to include a series elastic element in this assembly to reduce impact loads and to improve the bandwidth of torque and impedance control of the limb segment.